It is known to use cross-linked bitumen/polymer compositions, as coatings of various surfaces and, in particular, as road coatings, provided that these compositions exhibit in combination a certain number of mechanical characteristics. In order to maintain and/or improve the characteristics and in particular the mechanical properties of a conventional bitumen, cross-linked bituminous compositions have for a long time been used, in which the bitumen (formed from one or more types of bitumens) is mixed with one or more functional polymers, in particular styrene and butadiene elastomers, these elastomers being chemically cross-linked in situ, optionally using a coupling or cross-linking agent, for example sulphur or at least one of its precursors.
Optimized mechanical characteristics are in particular crucial for road coating applications. In addition to the mechanical properties, in the case of bitumens account should be taken of their susceptibility to certain chemical agents. These aggressive chemical agents can be, for example, hydrocarbon solvents, in particular petroleum-based solvents such as kerosenes, gas oils and/or gasolines or also products, in particular fluids, used for de-icing and/or defrosting and/or snow removal from aircraft and from taxiing zones. These fluids are for example aqueous saline solutions of potassium, sodium, magnesium and/or calcium, and/or compositions based on ethylene glycol and/or based on propylene glycol.
The aggressive effect of such chemical agents builds up with the stresses of intense traffic, in particular of heavy vehicles, and bad weather, which has the detrimental effect of increasing the rapid degradation of carriageways, in particular aircraft runways. This susceptibility of the bitumens to these aggressive chemical agents, to chemical attack is more particularly problematic for the bitumens constituting for example tarmacs and the coatings of airport runways, which are made of bituminous mixes (bitumen/aggregates conglomerate). In fact, these airport tarmacs and coatings are frequently soiled by drips of kerosene, during the filling of aircraft tanks, by leaks or other accidental spills of petroleum products. Moreover, they are also exposed to the different fluids used in cold weather to remove ice, frost and/or snow from aircraft and runways.
Service stations as well as industrial tank farms can also be subject to this same problem of the bituminous coatings' resistance to aggressive chemical agents such as hydrocarbon solvents and/or de-icing/defrosting/snow removal fluids. Conventional road carriageways are of course also exposed to this type of chemical attack.
In an attempt to remedy this, it has been proposed to incorporate various additives in bitumens. Thus the patent EP1311619 describes the use of waxes in bitumens for increasing their resistance to hydrocarbons. The waxes are in particular synthetic waxes originating from the Fischer Tropsch synthesis process. Said bitumens can optionally contain polymers which are not cross-linked.